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heron

Kohler M18S..cannot solve heat issue

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heron

This is in a 1989 DEUTZ.. 450hrs or so. Father in laws tractor. Have had an issue with hard starting when hot, replaced ignition coil and that was fixed. At the same time I noticed(he lives next door) that when he cuts and it's 90F out the tractor seems to "miss" and kind of a poofing sound. He is not mechanical so he just keeps cutting :((. I stopped him today and told him it needed to be fixed. We did notice that when we pulled out the choke a bit it seemed to solve it momentarily but then it just kept doing it and is really noticeable when under a load.

Plugs wires etc...electrical seem perfect. I had put on a new gas filter I got from Jacks for it that said it was a direct replacement when we got the tractor 18 or so months ago. I'm wondering if it could be a weak fuel pump that just acts up when hot. I already blew the lines out from the engine back thru the tank...seems to be no junk floating around. Tank cap has good vacuum hole so that is not it. Always run pure gas, no ethanol.

Would you go into the carb and check it first or replace the fuel pump? This tractor looks brand new but it still is an 89..maybe something is just decayed in the fuel pump.

I've got to get this running right as we are awaiting a roto tiller for it that has only be used about 5 times...it is coming with an 88 Sunstar that is in great shape but we'll not be keeping it.

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heron

I checked out the manual. I put some Seafoam in it tonight and ran it. I'll mess with the carb adjustments in the am and see if that may be the culprit. Seemed to run well at WOT tonight but again it is only 80F and not being worked.

I was just ready to take off the carb and give it a cleaning but honestly it looks really good.

I've got Seafoam and can try that.

Are these Walbro carbs known for getting gummed up pretty easily?

I think the original owner ran non ethanol gas also and took really good care of the machine.

Do you happen to know if I take off the carb and clean it I will have to replace all the gaskets or can I re-use them?

TY!

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heron

Yes..no issues there. I just meant when it gets hot it begins to sputter.

Its not the gas cap either. May be a sticky valve..?

I know there are quite a few things itn could be. Just trying to find someone who maybe has been thru the same situation.

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PeppyDan

The Sunstar series is know for having a complex wiring system and this could still be an electrical problem. One of my Sunstar's had one of the micro switches at the hydro control lever going bad and caused very similar symptoms. Unless you completely isolate the engines wiring from the tractor wiring you cannot rule out the wiring. Good luck in tracking the problem down!

Dan

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heron

Dan,

Interesting, I do notice it gets worse when the hydro is engaged although it also is being loaded.. How would one go about isolating the two systems? Sounds tricky.

I did notice today when it began to do it I opened the hood and checked the gas filter and there was maybe 1/8" of gas in it. The way the filter is situated it is almost level and then there is about 4" of line before it hooks to the pump.

I know the filter does not have to be "full" but I wonder if there is an acceptable amount that should be in the filter?

I'm leaning towards the pump being 25 years old and maybe it just cannot deliver adequate fuel when it's under demand...

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HubbardRA

The poofing sound may be a leaking head gasket. If the heads are not torqued properly, the gasket may seal when the engine is cold, but start to leak at high loads when the engine gets hot and the bolts elongate from the heat. I would suggest that you check the torque on the head bolts.

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HubbardRA

The poofing sound may be a leaking head gasket. If the heads are not torqued properly, the gasket may seal when the engine is cold, but start to leak at high loads when the engine gets hot and the bolts elongate from the heat. I would suggest that you check the torque on the head bolts.

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heron

On the head gasket wouldn't I see oil...smoke, oil usage up etc...?

None of that, plenty of power...hard to keep the tires from spinning when engaging hydro...way more torque than my Sunstar with the 20 Command.

When we had this issue before we found that it also would not start when it was hot. I thought the two issues...poofing and hot start were because of the coil.

Replaced the coil pack probably 10 hours ago back in the fall and the hot start issue quit and I thought the poofing was gone. Since the coils the machine starts with barely a touch of the key hot or cold so it definitely fixed one issue.

I've ordered one of the new Kohler plastic fuel pumps for like $35. I'm going to give that a try as it probably could use some help after 25 years anyway. I may go ahead and replace all the fuel line back to the tank and make sure all is clear in the tank.

Have any of you ever done the fuel pump on these Magnums? Will I have to remove the intake etc....?

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SmilinSam

With the head gasket , wouldn't be any smoke or oil usage. It would get just a little wet at the spot where it is not sealing, but would dry off when you shut the engine down.

Never had a poofing or whooshing sound with a bad coil. Just wont start.

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PeppyDan
quote:Originally posted by heron

Dan, Interesting, I do notice it gets worse when the hydro is engaged although it also is being loaded.. How would one go about isolating the two systems? Sounds tricky.I did notice today when it began to do it I opened the hood and checked the gas filter and there was maybe 1/8" of gas in it. The way the filter is situated it is almost level and then there is about 4" of line before it hooks to the pump. I know the filter does not have to be "full" but I wonder if there is an acceptable amount that should be in the filter?I'm leaning towards the pump being 25 years old and maybe it just cannot deliver adequate fuel when it's under demand...


id="quote">
id="quote">I wish I could tell you exactly how to check the switches but I got so frustrated with mine that I brought it to a local shop and he found the problem. I do remember that as soon as I pulled the lever away from the switches it would start missing and did not need to actually move the lever forward or reverse. I don't recall if he just bypassed the switch or if he replaced it.Dan

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stevenj

Wiring diagram for Sunstars

http://bsintek.basco.com/BriggsDocumentDisplay/jgEGGP_ezO0tG5ERl7mRgtLvBCd6.pdf

One of the Hydro control lever microswitches works with the operator presence switch under the seat. If you try and move the hydro lever and there is not an operator in the seat, the engine will shut off. Each one serves a different purpose and you'll have to trace the wiring diagram to figure them out.

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heron

On that head gasket...no wet spot what so ever...motor looks brand new everywhere and not a hint of an oil spot, the motor will not smoke at all under load.

All the cooling fins were cleaned out less than 10 hours ago when I had the motor out to replace the coil.

Anyone know if there is a screen of some type in the tank that could perhaps have something settling back on it? I did use compressed air back thru the line several times until I heard lots of bubbling in the tank. I shined a light in there after the vapor cleared and could see no debris floating around as I'd expect if something was plugged and I dislodged it with the air.

This carb is the Non adjustable type so all I have is the two screws and the one that does "richen" it up a bit seemed to not make a real change in how the motor sounds which again leads me down to the pump as a possible culprit. There are no air leaks as I have sprayed carb clean all around the intake and carb base.

I do have an 88 sunstar with a 16HP magnum on it's way to us for the rototiller. Supposedly the mower runs great so maybe I can switch some things around like the carb and see if it runs better or even microswitches on the hydrostat... ??

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heron
Originally posted by PeppyDan
quote:
id="quote">I'm not sure I would call it missing like it's cutting out. It definitely seems more like an air fuel mixture issue rather than an electrical cut out. I can hear the issue with it idling it's just not amplified as it is when I load the engine. Not sure how to describe the symptom other than "poofing" as if it's running out of gas or sucking air when it does it. I originally thought for sure it was the gas cap not ventilating...then replaced it, the gas filter..of course air filter. I even changed the gas out completely even though it was fresh non ethanol to begin with. I think before I replace the pump I may go ahead and pull the carb and just take the bowl off and check for junk, clean out the passages really well.

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Bruker

I've heard the "poofing" sound before also and it was a blown head gasket. Can you get your hand around or near where the head is attached to the cylinder and feel for a puff of air?

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heron

Not sure but I can check. I just find it hard to believe I'd have air without any oil residue but maybe there is some just starting.

Are these heads prone to losing the gasket easily.? This unit only has 477hrs on it and all original.

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Bruker
quote:Originally posted by heron

Not sure but I can check. I just find it hard to believe I'd have air without any oil residue but maybe there is some just starting.Are these heads prone to losing the gasket easily.? This unit only has 477hrs on it and all original.


id="quote">
id="quote">Does it backfire when you shut it off? I have to replace at least one head gasket in the Kohler Command engine in my father-in-laws Prestige every year because he won't shut it off at half-throttle.

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heron

No, plugs look very good with normal appearance. I may go ahead and change them out just to be safe. I cannot imagine it starting so well if the plugs were an issue but who knows.

On the backfire, no, never backfires and shuts down with no problems. My Kohler Command 20 in my 97 Sunstar will backfire every once in awhile.

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stevenj

Have you run a compression test on each cylinder? Have you tried new spark plugs yet? Does the poofing sound change if you run without the air cleaner? Perhaps an intake valve that is not fully sealing?

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heron

Poofing does not change when air cleaner off. Yes, I'm trying new plugs today. No compression test yet but may consider after plugs. No abundant oil consumption, no notable loss of power until when it begins to elicit symptoms.

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HubbardRA

Check your valve clearances. If a valve is too tight the engine will run fine when cold, but as the engine gets hotter the valve gets longer and will stop seating. It will be seated again after the engine cools down. I have fixed several engines with this problem. Put in the correct valve clearance and the engine is good to go.

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